1. Field of the Invention
This invention relates to methods and systems for determining the extent, respectively, of drainage water which flows into sewage pipes (inflow) and through seepage (infiltration) into sewer lines.
2. General Description of the Prior Art
It is unfortunately true that most of the sewer systems in this country, if not in the world, are overloaded during wet periods. Massive amounts of money have been appropriated in this country to assist cities in the expansion and/or repair of their sewer systems, and presently efforts are almost frantically being made to get on with this work. A major stumblingblock is that enormous quantities of surface drainage water are entering their systems; and before new sewage facilities can be adequately planned for and constructed, it is necessary to locate and do away with, or materially reduce, this non-sewage so that proper types and sizes of plants can be planned and built.
The first problem is, of course, that of identification of where the water is entering the lines, and second, whether it is caused by drain lines undesirably connected to sewer lines or by pipe leakage through cracks or faulty pipe joints. Insofar as the applicant is aware, efforts to solve these problems have at best involved uncoordinated, in time, measurements of fluid levels in manholes, and these have not been productive of a solution. For one thing, as a practical matter, fluid level in a manhole is a quite unreliable indice of flow through a particular manhole of a system. This follows since the size and shape of manholes and elevation and capacity of exit pipes from them are factors which influence the relation of fluid level to flow, and these parameters typically vary from manhole to manhole within a system.